1. Field of the Invention
The apparatus of the present invention generally relates to communication networks, and more particularly to establishing connections between a plurality of requestors for use of a plurality of resources being shared by requestors.
2. Description of the Prior Art
In some computer communications systems, the delays entailed in message transmission and processing may be unknown, and messages may even be lost. Resources may be unable to service requests. Despite this, it is essential that all elements of a communication system have a consistent view of the state of the system, to prevent errors in system operation.
As an example of an inconsistent view, consider a system in which (a) one processor sends a request message and assumes that the request has been rejected unless an acceptance message arrives within 1 msec., (b) a processor (resource) that can service that request may take as long as 2 msec. to reply to a request message, and (c) a resource remains committed to a requestor once it has sent an acceptance message. Clearly, if a resource (a processor that provides a service) takes more than 1 msec. to reply to a request, the requestor believes its request has been rejected and goes on to other work, and the resource believes it is committed to the requestor and waits indefinitely for further messages from the requestor. This is an inconsistent view of the system state due to unpredictable delays in message handling. It results in an error in system operation. It is especially difficult to maintain a consistent view when more than one resource in the communication network is capable of servicing a request.